E36 Transmission Stuck in 3rd gear
 

1993 325i - I have an auto transmission that slips into "limp mode"(stuck in 3rd gear) shortly after running. Intially the pressure regulator was replaced with no inprovement or change in symptoms. The transmission was then replaced with a used unit which subsequently had the same problem.

I discussed with the independent mechanic that it sounds more like a logic issue than mechanical one so he replaced the main CPU with a borowed one from a known good car and the problem remains with the transmission. Therfore, he replaced the transmission a third time and it too has the same problem (each time this occurs I am charged with 10hrs labor - $4,000 to this point).

The independent mechanic and local BMW dealer insist the problem is truly a defective transmission and the only solution is to be able to eventually find one without the problem. Because the transmissions otherwise operate flawlessly, my belief is that BMW unknowingly assembled these cars with a defective transmission sending unit which misinterprets a pressure, fluid level or temperature and sends an incorrect code.

In an effort to solve this problem myself and stop the bleeding, I believe that if I can identify which wire these signals are transmitted on I can override the error with an appropriate high/low voltage or ground. In other words, I believe the symptoms are being misdiagnosed. Thoughts?

I would assume, even tough assumptions can be dangerous, that after the 1st repait the subsequent ones should be 'on the house' until they get it right. That's how it's always been for me anyhow (of course I raise holy hell when a mechanic does work and doesn't fix the problem... especially from the 3rd time on)

Do you have the ETM for your car? You should be able to track down the correct wire(s) with that.

after 3 transmissions - I question your mechanic - he might be good at unbolting & bolting things together but has he thought of trans range switch (under console) ? If shifter gets cuaght between gears it throws same code and goes into "limp mode". They go bad from wear & tear but also when someone spills liquid in console area. :beer

Maybe a long shot, but see if this might be of some help, relevance...
http://www.bmwe34.net/E34main/Trouble/TransProgram.asp . Good luck.

Thank you for your speedy replies as they are very educaitonal. A characteristic of the transmission now is that it quickly faults to limp mode during rain (which aligns with the connection suggestions) and when I get it out on the freeway (regardless of weather) it will remain in correct mode during the whole drive (up to three hours during last trip). I will bring all of this to the mechanics attention and suggest he misdiagnosed the symptoms from the beginning.

Cleaned the wiring harness and connectors - no problem for weeks - thank you, sirs

Hello, this is my first post on this forum and I realize this is an old thread but I am having a similar problem. Are the connectors you cleaned in the console or the ones that connect to the transmission?

Thanks,
Kevin

The ones that connect to the transmission.

OK, I will clean them and keep you all posted. I also read something about the aux fan having an effect on the transmission going into limp mode. This car was wrecked and I have not yet reinstalled that fan so does anyone know - will a missing aux fan put the tranny into failsafe?

Thanks a lot for usefull information. my e36 320i touring (1995) is having similar problem and i do not know what to do. the technician says is the solenoid wave problem, anyone with usefull idea!

Did the tech scan the OBD system for Diagnostic Trouble Codes (DTC)? If a solenoid failed it would trigger a DTC. They wont always cause a CEL to illuminate. A quick scan of the OBD system will help reveal any issues.